GB2275007A

GB2275007A - Abrasive element

Info

Publication number: GB2275007A
Application number: GB9303049A
Authority: GB
Inventors: David Leslie Crump; Christopher Robert North
Original assignee: Unicorn Abrasives UK Ltd
Current assignee: Saint Gobain Abrasives Ltd
Priority date: 1993-02-16
Filing date: 1993-02-16
Publication date: 1994-08-17
Anticipated expiration: 2013-02-16
Also published as: GB9303049D0; GB2275007B

Abstract

An abrasive disc or other element for use on a sanding machine comprises a backing sheet (3) to the back of which there is attached a release sheet (4). The sheet (3) comprises a body portion (1) and a detachable tab (2), the tab being connected to the body portion by bridge portions (7). Preferably the bridge portions are separated by enclosed slots (8). <IMAGE>

Description

ABRASIVE ELEMENTS The invention relates to abrasive elements and in particular to such elements having an adhesive backing by which they may be secured to a support. One specific example is an abrasive disc for use on a sanding machine and for convenience the invention will be described, by way of example, with reference to abrasive discs. A release sheet is secured to the adhesive backing for storage and transport and is released by the operator to enable the disc to be stuck on to the sanding machine. A detachable tab portion is present to enable the release sheet to be peeled off in a convenient way.

It is one object of this invention to provide an element as defined having an easily detachable tab portion and which can be made easily and economically.

According to the invention in one aspect there is provided an abrasive element comprising a backing sheet having a layer of abrasive material coated on a top surface, and adhesive on the bottom surface, a release sheet attached to the bottom surface, the element comprising a body portion and a detachable tab portion characterised in that the tab portion is connected to the body portion by bridge portions formed in the backing sheet and the release sheet.

Preferably the tab portion is detached from the body portion at the bridge portions formed in the backing sheet.

Preferably the release sheet comprises a film which is more elastic than the backing sheet. By way of example, the extensibility, i.e. a tensile elongation at break of the film is from about 100 to about 1200%, preferably about 150% to about 700%, most preferably about 200% to about 300%. (By contrast the same characteristic for the abrasive sheet is about 2 to 25%).

The release sheet may be selected from a wide range of materials such as suitable polyethylene, polypropylene, polyethylene terephthalate, PTFE, flexible polyvinyl chloride, ethylene vinylidene acetate (EVA), crimped paper, perfluoroallcoxy polymer, polyvinylfluoride, polyvinylidene fluoride, polytrichlorethylene; copolymers and derivatives thereof. Preferably the release sheet comprises a siliconised plastics, more preferably a siliconised polyethylene. Because the release sheet is more elastic or extensible than the backing sheet the cutting of the bridge portions in the backing sheet and the release sheet may be done using a simple and relatively crude cutting tool.

The tab is easily detachable from the body portion. When the tab portion is pulled the backing sheet portion thereof separates from the backing sheet of the body portion while the release sheet portion still remains integral with that of the body portion, so that the release sheet separates from the body portion.

In another aspect, the invention provides a method of making an element of the invention comprises forming a sandwich of the backing sheet and release sheet, cutting the element of the intended shape and perforating the region between the body and the tab portion to form the bridge portions. Preferably the cutting is done using a cutting knife having spaced apart cutting teeth to form enclosed slots adjacent ones of which define the bridge portions.

In order that the invention may be well understood it will now be described by way of example with reference to the accompanying diagrammatic drawings in which Figure 1 is a top plan view of one abrasive disc of the invention; Figure 2 is an exploded plan view of the area "A" shown in Figure 1; Figure 3 is an elevation showing a stage of detaching the release sheet from the disc body; Figure 4 is an elevation taken on lines IV - IV on Figure 3; and Figure 5 is an elevation of a cutter blade The abrasive disc shown comprises a disc body 1 and a detachable tab portion 2. The disc is a sandwich or lamination of a backing sheet 3 and a release sheet 4. The backing sheet 3 has a top or outer face coated with abrasive particles 5 e.g. aluminium oxide, silicon carbide or the like, bonded to each other and to the backing sheet 3 by a resin or like binder.The backing sheet 3 is a paper, textile, plastics sheet, fibre or the like. The bottom or inner face is coated with a contact adhesive 6 by which the disc may be adhered to the support of a sanding machine, not shown. The release sheet 4 is formed of a material which is significantly more extensible than the backing sheet 3. The release sheet 4 may be formed of a natural or synthetic material e.g. a siliconised plastics, e.g. siliconised polyethylene or other material mentioned earlier. The adhesive 6 may be an acrylate, silicone, natural or synthetic rubber; or the like.

The adhesive may be applied by direct coating or during a lamination.

The release tab portion 2 is joined to the disc body 1 by a number of radial bridge portions 7 separated by intermediate enclosed slots 8. The slots are formed by a perforated cutter blade 9 shown in Figure 5 and having cutter teeth 10. The cutter blade may form part of a relatively simple or crude cutter device such a strip steel knife board or a roller press, a reciprocating press, a travelling head press, a clicker press or the like. The cutter teeth are set proud of the main body cutter such that they cut more deeply. As the cutter teeth pass through the backing sheet, sufficient depth of cut is achieved for the blade thickness to provide a wedge action which forces the tab portion 2 to detach from the disc body in the backing sheet 3, at the bridge portions 7. Because the release sheet is many times more extensible than the backing sheet, it remains attached to the disc body at the bridge portions.

In use, the operator grabs the tab portion 2, pulling it from the body portion 1. The backing sheet portion 3 of the tab portion 2 detaches itself easily from the backing sheet of the main body portion 1 whereas the release sheet portion of the tab portion remains attached to the release sheet proper allowing for easy and clean separation of the release sheet.

The invention is not limited to the embodiment shown; for example the element need not be circular but can be rectangular.

Claims

1. An abrasive element comprising a backing sheet (3) having a layer (5) of abrasive material coated on a top surface, and adhesive (6) on the bottom surface, a release sheet (4) attached to the bottom surface, the element comprising a body portion (1) and a detachable tab portion (2) characterised in that the tab portion (2) is connected to the body portion (1) by bridge portions (7) formed in the backing sheet (3) and the release sheet (4).

2. An element according to Claim 1, wherein the release sheet (4) comprises a film which has more extensibility than the backing sheet (3).

3. An element according to Claim 1, wherein the release sheet (4) comprises a siliconised plastics.

4. An element according to Claim 3, wherein the release sheet (4) comprises a siliconised polyethylene.

5. An element according to any preceding Claim, wherein the bridge portions (7) are separated by enclosed slots (8).

6. An element according to any preceding Claim, wherein the tab portion (2) is detached from the body portion (1) at the bridge portions formed in the backing sheet (3).

7. A method of making an element according to any preceding Claim, comprising forming a sandwich of the backing sheet (3) and release sheet (4) and cutting the element of the intended shape and perforating the region between the body (1) and the tab portion (2) to form the bridge portions (7).

8. A method according to Claim 7, wherein the cutting is done using a cutting knife (9) having spaced apart cutting teeth (10) to form enclosed slots (8) adjacent ones of which define bridge portions (7).

9. A method according to Claim 8, wherein the cutter teeth (10) are set sufficiently proud of the cutter body to exert a wedging effect to detach the tab portion (2) from the disc body (1) in the backing sheet (3) at the bridge portions (7).